Disk defragging can make a serious difference between a slow machine and a fast one. The art of defragging, however, has stumped some SearchWindowsManageability users. They're confused about when and what to defrag and the defrag glitches they encounter. SWM's resident defrag expert, Frank Alperstaedt, managing director of Berlin, Germany-based defrag software maker O & O Software, GmbH, has been answering these basic, yet puzzling, user questions. Here are Alperstaedt's answers to IT professionals' most-frequently-asked questions.
User problem #1: I have a good understanding of how disk drives and file systems work. I have no difficulty understanding the typical single drive defragmentation process. I also understand the various RAID technologies. Put them together and I get a real mental block. Do you have an explanation?
Alperstaedt: Let's start with a plain hard disk. Files are written in chunks of data. When you are not lucky (e.g. the disk gets full or you have had many deletions and creations of new files) these chunks are not continuously placed on the disk. The more small files you have, the more files might get fragmented and performance suffers. Also, you may face the so-called free space fragmentation, where free space is scattered throughout the disk. This leads to a higher fragmentation of newly created files since these are placed in the "holes" right from the beginning. This also causes severe performance penalties. That was easy, wasn't
Okay, now imagine a RAID 5 system is writing a file. EVERY file will be broken up into pieces and placed on various hard disks including checksums. etc. Therefore, every file will be split into smaller pieces. Can you already guess what will occur? BINGO! The free space fragmentation can be a significant impact on your system. Even worse, the fragmentation of all files due to the smaller size of their chunks can increase. But this depends on your system as well as on the usage. So, you actually need a defrag software even more when using RAID compared to regular hard disks. Just give it a try and you will see!
User problem #2: Will defragging my home PC completely get rid of all of the files that were previously deleted from the recycling bin?
Alperstaedt: No, defragging a drive does not free up space! It consolidates the fragmented files and frees up larger continuous space on the disk.
User problem #3: I tried two times to defrag. Both times the bar went to 10% and stayed there. The last time I let it sit for five hours, and it did not move past the 10%. Any suggestions?
Alperstaedt: This could be related to several things. First, the file might be locked. Usually, a defragger tries several times to move the file and finally skips it. Another reason could be that there is not enough continuous free space left, and the defragger tries to free some space by moving other files out of the way. Those are the most common reasons. To give you a more founded answer, we need to have a closer look at the specific configuration of your system.
User problem #4: Is there a need for defragging when you have a SAN? What are good practices for defragging when you have a SAN?
Alperstaedt: You can bring defragging down to the simple machine, where everything is stored. Check your servers for capacity and workload. You can simply apply the same procedures and rules as defragging a single server. But keep in mind that your SAN structure might rely on availability of some servers, so scheduling defragging should be done carefully! Some defraggers watch the computer's activity and adjust their resource usage accordingly. This might be a very good idea for your situation!
User problem #5: Can I defrag a SCSI drive?
Alperstaedt: Yes, you can. There is no difference between a SCSI and an IDE drive, from Windows' and a defragger's point of view. The only difference that would matter is the file system (FAT or NTFS). SCSI usually provides better performance, so you should be able to get the defragmentation done even quicker.
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